Methods and compositions for the prevention and treatment of anemia

ABSTRACT

Methods for increasing and maintaining hematocrit in a mammal comprising administering a hyperglycosylated analog of erythropoietin are disclosed. An analog may be administered less frequently than an equivalent molar amount of recombinant human erythropoietin to obtain a comparable target hematocrit and treat anemia. Alternatively, a lower molar amount of a hyperglycosylated analog may be administered to obtain a comparable target hematocrit and treat anemia. Also disclosed are new hyperglycosylated erythopoietin analogs, methods of production of the analogs, and compositions comprising the analogs.

This application is a divisional of application Ser. No. 09/723,955,filed Nov. 27, 2000, allowed, which is a continuation of applicationSer. No. 09/559,001, filed Apr. 21, 2000, pending, which is acontinuation-in-part of application Ser. No. 09/178,292, filed Oct. 23,1998, abandoned, which are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to increasing hematocrit in a mammal usinghyperglycosylated analogs of erythropoietin. More particularly, theinvention relates to less frequent dosing of a hyperglycosylated analogcompared to recombinant human erythropoietin to raise and maintainhematocrit and treat anemia. The invention also relates toadministration of lower amounts of a hyperglycosylated analog comparedto recombinant human erythropoietin at an equivalent dosing frequency inorder to raise and maintain hematocrit and treat anemia. Newhyperglycosylated analogs of erythropoietin are also provided.

BACKGROUND OF THE INVENTION

Erythropoietin (Epo) is a glycoprotein hormone necessary for thematuration of erythroid progenitor cells into erythrocytes. It isproduced in the kidney and is essential in regulating levels of redblood cells in the circulation. Conditions marked by low levels oftissue oxygen signal increased production of Epo, which in turnstimulates erythropoiesis. A loss of kidney function as is seen inchronic renal failure (CRF), for example, typically results in decreasedproduction of Epo and a concomitant reduction in red blood cells.

Human urinary Epo was purified by Miyake et al. (J. Biol. Chem. 252,5558 (1977)) from patients with aplastic anemia. However, the amount ofpurified Epo protein obtained from this source was insufficient fortherapeutic applications. The identification and cloning of the geneencoding human Epo and expression of recombinant protein was disclosedin U.S. Pat. No. 4,703,008 to Lin, the disclosure of which isincorporated herein by reference. A method for purification ofrecombinant human erythropoietin from cell medium is disclosed in U.S.Pat. No. 4,667,016 to Lai et. al., which is incorporated herein byreference. The production of biologically active Epo from mammalian hostcells has made available, for the first time, quantities of Epo suitablefor therapeutic applications. In addition, knowledge of the genesequence and the increased availability of purified protein has led to abetter understanding of the mode of action of this protein.

Both human urinary derived Epo (Miyake et al. supra) and recombinanthuman Epo expressed in mammalian cells contain three N-linked and oneO-linked oligosaccharide chains which together comprise about 40% of thetotal molecular weight of the glycoprotein. N-linked glycosylationoccurs at asparagine residues located at positions 24, 38 and 83 whileO-linked glycosylation occurs at a serine residue located at position126 (Lai et al. J. Biol. Chem. 261, 3116 (1986); Broudy et al. Arch.Biochem. Biophys. 265, 329 (1988)). The oligosaccharide chains have beenshown to be modified with terminal sialic acid residues with N-linkedchains typically having up to four sialic acids per chain and O-linkedchains having up to two sialic acids. An Epo polypeptide may thereforeaccommodate up to a total of 14 sialic acids.

Various studies have shown that alterations of Epo carbohydrate chainscan affect biological activity. In one study, however, the removal ofN-linked or O-linked oligosaccharide chains singly or together bymutagenesis of asparagine or serine residues that are glycosylationsites sharply reduces in vitro activity of the altered Epo that isproduced in mammalian cells (Dube et. al. J. Biol. Chem. 263, 17516(1988)). However, DeLorme et al. (Biochemistry 31, 9871-9876 (1992))reported that removal of N-linked glycosylation sites in Epo reduced invivo but not in vitro biological activity.

The relationship between the sialic acid content of Epo and in vivobiological activity was disclosed by determining the in vivo activity ofisolated Epo isoforms. It was found that a stepwise increase in sialicacid content per Epo molecule gave a corresponding stepwise increase inin vivo biological activity as measured by the ability of equimolarconcentrations of isolated Epo isoforms to raise the hematocrit ofnormal mice (Egrie et al. Glycoconjugate J. 10, 263 (1993)). Those Epoisoforms having higher sialic acid content also exhibited a longer serumhalf-life but decreased affinity for the Epo receptor, suggesting thatserum half-life is an important determinant of in vivo biologicalactivity.

Introduction of new glycosylation sites in the Epo polypeptide canresult in the production of molecules with additional carbohydratechains. See PCT Publication Nos. WO91/05867 and WO94/09257 herebyincorporated by reference in their entirety. Epo glycosylation analogshaving at least one additional N-linked carbohydrate chain and/or havingat least one additional O-linked carbohydrate chain are disclosed. Aglycosylation analog having one additional N-linked chain was determinedto have a longer circulating half-life compared to recombinant human Epo(rHuEpo) (isoforms 9-14) and to a purified isoform of rHuEpo having 14sialic acids per molecule.

Administration of recombinant human erythropoietin (rHuEpo) is effectivein raising red blood cell levels in anemic patients with end stage renaldisease (Eschbach et al. New Eng. J. Med. 316, 73-38 (1987)). Subsequentstudies have shown that treatment with rHuEpo can correct anemiaassociated with a variety of other conditions. (Fischl et al. New Eng.J. Med. 322, 1488-1493 (1990); Laupacis, Lancet 341, 1228-1232 (1993).Regulatory approvals have been given for the use of rHuEpo in thetreatment of anemia associated with CRF, anemia related to therapy withAZT (zidovudine) in HIV-infected patients, anemia in patients withnon-myeloid malignancies receiving chemotherapy, and anemia in patientsundergoing surgery to reduce the need of allogenic blood transfusions.Current therapy for all approved indications (except the surgeryindication) involves a starting dose of between 50-150 Units/kg threetimes per week (TIW) administered either by an intravenous (IV) orsubcutaneous (SC) injection to reach a suggested target hematocritrange. For the surgery indication, rHuEpo is administered every day 10days prior to surgery, on the day of surgery, and four days thereafter(EPOGEN® Package Insert, Dec. 23, 1996). In general, the currentrecommended starting doses for rHuEpo raise hematocrit into the targetrange in about six to eight weeks. Once the target hematocrit range hasbeen achieved, a maintenance dosing schedule is established which willvary depending upon the patient, but is typically three times per weekfor anemic patients with CRF. The administration of rHuEpo describedabove is an effective and well-tolerated regimen for the treatment ofanemia.

It would be desirable to have a therapeutic with greater potency thanrHuEpo. An advantage to such a molecule would be that it could beadministered less frequently and/or at a lower dose. Current treatmentsfor patients suffering from anemia call for administration of EPOGEN®three times per week and for surgery patients administration once perday. A less frequent dosing schedule would be more convenient to bothphysicians and patients, especially those patients who do not makeregularly scheduled visits to doctor's offices or clinics, or those whoself-inject their Epo. Another advantage of a more potent molecule isthat less drug is being introduced into patients for a comparableincrease in hematocrit.

It is therefore an object of the invention to identify more potentmolecules for the treatment of anemia which will permit a less frequentdosing schedule. It is a further object of the invention to providemolecules which will increase and maintain hematocrit at levels whichare at least comparable to that of Epo when administered at a lowerdose. It is also an object of the invention that these moleculesselected for less frequent dosing is at least as well tolerated asrHuEpo and potentially better tolerated in some patients.

SUMMARY OF THE INVENTION

It has been found that a hyperglycosylated Epo analog designated N47(Asn³⁰Thr³²Val⁸⁷Asn⁸⁸Thr⁹⁰ Epo) has a longer serum half-life thanrecombinant human erythropoietin (rHuEpo) and a greater in vivo activitywhen administered at the same dose and frequency as rHuEpo. Further, theanalog has been shown to raise hematocrit in mice at once per weekadministration that is comparable to hematocrit rise for rHuEpoadministered three times per week. The pharmacokinetics of Epo analogN47 administered to mice and to humans were similar.

The invention provides for a method of raising and maintaininghematocrit in a mammal comprising administering a therapeuticallyeffective amount of an Epo hyperglycosylated analog in a pharmaceuticalcomposition, wherein the analog is administered less frequently than anequivalent molar amount of rHuEpo to obtain a comparable targethematocrit. The dosing frequency of the present invention in order toreach a patient's optimal hematocrit range is less than three times perweek. Dosing frequencies may be two times per week, one time per week,or less than one time per week, such as one time every other week, onceper month or once every two months. The dosing frequency required tomaintain a patient's target hematocrit is less than three times perweek. Dosing frequencies may be two times per week, one time per week,or less than one time per week, such as one time every two weeks, onceper month or once every two months.

The invention also provides for a method of raising and maintaininghematocrit in a mammal comprising administrating a therapeuticallyeffective amount of an Epo hyperglycosylated analog wherein the analogis administered at a lower molar amount than rHuEpo to obtain acomparable target hematocrit.

Also provided for are pharmaceutical compositions comprising Epohyperglycosylated analogs wherein the compositions are suitable fordosing frequency of less than three times per week. The compositionswill include pharmaceutically acceptable adjuvants suitable for use withEpo hyperglycosylated analogs.

The invention may be employed with any condition resulting in a decreasein red blood cell levels, such as anemia associated with a decline orloss of kidney function, (chronic renal failure) myelosuppressivetherapy, cancer, viral infection, chronic disease and excessive loss ofblood during surgical procedures. In one embodiment, treatment with onceper week dosing, or less frequently, is for anemia resulting fromchronic renal failure.

Also provided for are new hyperglycosylated analogs of Epo. The analogscomprise at least one additional carbohydrate chain compared to rHuEpowherein at least one N-linked carbohydrate chain is added at any ofpositions 52, 53, 55, 86 and 114. New hyperglycosylated analogs may havetwo, three or four additional carbohydrate chains, or may have more thanfour additional chains.

DESCRIPTION OF THE FIGURES

FIG. 1 shows the amino acid sequence of human erythropoietin.

FIG. 2 shows a Western blot analysis of rHuEpo and Epo hyperglycosylatedanalogs from CHO cell expression in serum free medium. Construction ofanalogs N53 and N61 are described in Example 1. The number of N-linkedcarbohydrate chains on each analog is indicated.

FIG. 3 compares the activity of rHuEpo, Epo analogs N4, N18, and N50(containing four N-linked carbohydrate chains), N47 (containing fiveN-linked carbohydrate chains), and N53 (containing six N-linkedcarbohydrate chains) in the exhypoxic polycythemic mouse bioassay.Experimental procedures are described in Example 3. Each pointrepresents the mean response of five animals. Analogs N4, N18 and N47have been described previously in WO94/09257.

FIG. 4 compares the serum half-life of rHuEpo and Epo analog N47administered to normal rats by intravenous injection (IV). Experimentalprocedures are described in Example 4. Results are the mean(±SD) foreach group.

FIG. 5 compares the serum half-life of rHuEpo and Epo analog N47administered to Beagle dogs by intravenous injection (IV). Experimentalprocedures are described in Example 4. Results are the mean(±SD) foreach group.

FIG. 6 shows the increase in hematocrit in mice in response to varyingdoses of rHuEpo or Epo analog N47 administered by intraperitonealinjection (IP) three times per week (TIW) for six weeks. Experimentalprocedures are described in Example 5. Results shown are the groupmean(±SD) of the change in hematocrit for each dose group.

FIG. 7 compares the relative potency in mice of rHuEpo and Epo analogN47 injected by either the intraperitoneal (IP) or intravenous (IV)routes of, administration at a frequency of once weekly (QW) or threetime a week (TIW). Experimental procedures are described in Example 5.Each point represents the mean(±SD) of data from separate experiments asfollows:

N47, IP, TIW (n=5); N47, IV, TIW (n=1); N47, IP, QW (n=2); N47, IV, QW(n=3); rHuEpo, IP, TIW (n=5); rHuEpo, IV, QW (n=2). Each experiment used7-13 mice per dose.

FIG. 8 shows the increase in hematocrit in mice in response to varyingdoses of rHuEpo or Epo analog N47 administered by intravenous (IV)injection one time per week (QW) for approximately six weeks.Experimental procedures are described in Example 5. Results shown arethe group mean(±SD) of the change in hematocrit for each dose group.

FIG. 9 shows the increase in hematocrit in mice in response to varyingdoses of Epo analog N47 administered by intravenous (IV) injection onetime per week (QW) or once every other week (EOW) for approximately sixweeks. Experimental procedures are described in Example 5. Results shownare the group mean(±SD) of the change in hematocrit for each dose group.

FIG. 10 shows the amino acid sequence of the hinge, CH2 and CH3 regionsof human IgGγ1.

FIG. 11 shows the cDNA and amino acid sequence of Epo N47-Fc fusionpolypeptide including the Epo signal sequence. The amino terminal Fcresidue is fused to the arg-166 residue of Epo.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides for a method of raising and maintaininghematocrit comprising administering a therapeutically effective amountof a hyperglycosylated analog of erythropoietin in a pharmaceuticalcomposition. The analog is administered less frequently than anequivalent molar amount of rHuEpo to obtain a comparable targethematocrit. The invention also provides for a method of raising andmaintaining hematocrit comprising administering a hyperglycosylatedanalog in lower molar amounts than rHuEpo to obtain a comparable targethematocrit. The composition may be administered by intravenous,subcutaneous or intraperitoneal routes.

Surprisingly, it has been found that analog N47, a hyperglycosylated Epoanalog described in WO94/09257, could achieve an increase in hematocritadministered once a week that was comparable to that observed for rHuEpogiven three times per week. Analog N47 has the following amino acidchanges: ala to asn at 30; his to thr at 32; pro to val at 87; trp toasn at 88; and pro to thr at 90 which resulted in the addition of twoN-linked carbohydrate chains at asparagine residues 30 and 88. Theanalog was expressed in Chinese hamster ovary (CHO) cells (as describedin Example 1) and purified as described in Example 2 to give isoforms of17 to 22 sialic acids. Analog N47 showed a greater serum half-life inrats and beagle dogs than rHuEpo when injected intravenously (FIGS. 4and 5). When injected intraperitoneally three times per week, N47induced increases in hematocrit of normal mice comparable to rHuEpo atlower concentrations (FIG. 6). The potency of N47 was demonstrated to beabout 3 to 4-fold higher than rHuEpo when administered three times perweek (FIGS. 6 and 7). When given once per week, at similar doses, rHuEposhowed little stimulation of hematocrit in normal mice while N47 gave amarked increase (FIG. 8). The potency of N47 was about 14-fold higherthan rHuEpo for once per week dosing (FIG. 7). Significantly, thehematocrit response for analog N47 given once per week is comparable tothat for rHuEpo given three times per week. Even when administered onceevery other week, N47 still produced significant increases in thehematocrit of normal mice (FIG. 9). Taken together, the data indicatedthat Epo hyperglycosylated analogs, and analog N47 in particular, can beused advantageously to raise hematocrit using less frequent dosing thanfor current treatment with rHuEpo.

It has also been shown that the results described above obtained in micemay be extrapolated to humans. Pharmacokinetic parameters foradministration of rHuEpo and analog N47 to 11 Continuous AmbulatoryPeritoneal Dialysis (CAPD) patients demonstrate that analog N47 has athree-fold longer serum half-life than rHuEpo (Example 6 and Table 5).These results suggest that Epo hyperglycosylated analogs allow lessfrequent dosing than rHuEpo in humans.

As used herein, the term “hyperglycosylated Epo analog” refers to Epocomprising at least one additional glycosylation site with an additionalcarbohydrate chain added to the site. Glycosylation sites may be forN-linked or O-linked carbohydrate chains. New N-linked glycosylationsites are introduced by alterations in the DNA sequence to encode theconsensus site for N-linked carbohydrate addition (the amino acidsAsn-X-Ser/Thr) in the polypeptide chain, while new O-linked sites areintroduced by alterations in the DNA sequence to encode a serine or athreonine residue. The analogs are constructed by mutagenesis techniquesfor introducing additions, deletions or substitutions of amino acidresidues that increase or alter sites in the Epo polypeptide that areavailable for glycosylation. DNA encoding an Epo hyperglycosylatedanalog is transfected into a eucaryotic host cell and the expressedglycoprotein is analyzed for the presence of an additional carbohydratechain.

Epo hyperglycosylated analogs have shown in vitro activity which wascomparable to or even less than that determined for rHuEpo, suggestingthat binding to the Epo receptor is not enhanced, and may in some casesbe diminished, by addition of carbohydrate chains. However,hyperglycosylation can typically increase serum half-life andpotentially lead to increased in vivo biological activity. One Epoanalog having an additional N-linked carbohydrate chain at position 88exhibited decreased affinity for receptor compared to rHuEpo (isoforms9-14) or to a purified isoform of rHuEpo having 14 sialic acids permolecule, yet demonstrated a longer circulating half-life and enhancedin vivo activity compared to either a mixture of Epo isoforms 9-14 orisolated Epo isoform 14.

The Epo hyperglycosylated analogs which may be administered according tothe present invention will have at least one additional N-linked orO-linked carbohydrate chain. In one embodiment, the analogs will havetwo additional N-linked carbohydrate chains. In other embodiments, theanalogs will have three, four or more additional N-linked carbohydratechains. As examples, the analogs of the invention will have at least oneadditional N-linked chain at one or more of amino acid residues 30, 51,57, 69, 88, 89, 136 and 138 of the sequence of human Epo. In oneembodiment, the analog has additional N-linked carbohydrate chains atresidues 30 and 88 of human Epo. The numbering of amino acid residues ofhuman Epo is as shown in FIG. 1 and SEQ ID NO:1. FIG. 1 shows apredicted mature Epo polypeptide of 166 amino acids whereas recombinantproduced Epo has 165 amino acids after removal of the C-terminalarginine residue. It is understood that rHuEpo and hyperglycosylated Epoanalogs may have either 165 or 166 amino acids.

The analogs of the invention will have at least four N-linkedcarbohydrate chains. Of the four chains, three may be at the naturallyoccurring sites at positions 24, 38, and 83. However, it is contemplatedthat some analogs of the invention may have alterations of one or moreof the naturally-occurring glycosylation sites such that one or more ofthe sites are deleted and substituted with a new site. Such analogs arealso provided by the invention. For example, any one of sites atpositions 24, 38 and 83 may be deleted and substituted with a site atposition 88. Optionally, the analogs may have an O-linked site atposition 126.

The invention also provides for new Epo hyperglycosylated analogs havingat least one additional carbohydrate chain. It has been found that anadditional N-linked carbohydrate chain is added at any of positions 52,53, 55, 86 and 114 which have been modified to be a glycosylation site.Specific embodiments include analogs N49 through N61 as described inTable 1. The new analogs will have at least one new N-linkedglycosylation site at any of positions 52, 53, 55, 86 and 114 and mayfurther comprise additional N-linked or O-linked carbohydrate chains atother sites. The analogs may have one, two, three or four additionalcarbohydrate chains, or more than four additional chains. In onepreferred embodiment, the analogs will have three additional N-linkedcarbohydrate chains (six N-linked chains total). In another preferredembodiment, the analogs will have four additional N-linked chains (sevenN-linked chains total). The analogs having three or four, or more thanfour, additional N-linked carbohydrate chains may have, but are notlimited to, an additional chain at any of positions 52, 53, 55, 86 and114.

Surprisingly, it has been found that a hyperglycosylated analog withthree additional N-linked chains at positions 30, 53 and 88 (sixN-linked chains total) has a greater in vivo activity than analog N47with two additional chains (five total). The results are shown in FIG.3. It is clear that the in vivo activity of the analogs is directlydependent on the number of N-linked carbohydrate chains. These resultsmay be extrapolated to the therapeutic setting wherein the analogshaving more N-linked carbohydrate chains than N47 may be dosed even lessfrequently.

In addition, the invention provides for hyperglycosylated Epo analogswith three additional N-linked chains at positions 30, 55 and 88; 30, 55and 114; and 30, 88 and 114. Epo analogs with four additional N-linkedchains or three additional N-linked chains and one additional O-linkedchain at position 125 are also provided.

The analogs may be prepared by a variety of mutagenesis techniquesavailable to one skilled in the art, such as site-directed mutagenesis,PCR mutagenesis and cassette mutagenesis (Zoller et al. Meth. Enz. 100,468-500 (1983); Higuchi, in PCR Protocols pp. 177-183 (Academic Press,1990); Wells et al. Gene 34, 315-323 (1985)). Example 1 describes theuse of PCR mutagenesis techniques to construct new Epo hyperglycosylatedanalogs.

An Epo DNA sequence which has undergone mutagenesis is inserted into anexpression vector using standard techniques with the vector beingsuitable for maintenance in a mammalian host cell. The vector willtypically contain the following elements: promoter and other “upstream”regulatory elements, origin of replication, ribosome binding site,transcription termination site, polylinker site, and selectable markerthat are compatible with use in a mammalian host cell. Vectors may alsocontain elements that allow propagation and maintenance in procaryotichost cells as well.

Suitable cells or cell lines include any from mammalian sources,including human sources. Examples include COS-7 (ATCC accession no. CRL1651), human 293, baby hamster kidney (BHK, ATCC accession no. CCL 10),Chinese hamster ovary cells (including dihydrofolate reductase(DHFR)-deficient cells, Urlab et al. Proc. Natl. Acad. Sci. USA 77,4216-4220 (1980)) Other suitable mammalian cell lines include, but arenot limited to, HeLa, mouse L-929 and 3T3. In a preferred embodiment,DHFR-deficient CHO cells are used.

Vectors comprising sequences encoding Epo hyperglycosylation analogs areintroduced into host cells by standard transformation or transfectiontechniques. Culturing, amplifying and screening transformed ortransfected host cells are accomplished using publicly available methods(Gething et al. Nature 293, 620-625 (1981); Kaufman et al. Mol. Cell.Biol. 5, 1750-1759 (1985); U.S. Pat. No. 4,419,446). Host cellsharboring DNA sequences encoding Epo hyperglycosylated analogs arecultured under conditions that permit expression of the analogs. Theanalogs are recovered from the cell media and purified using proceduresessentially as described previously (WO94/09257) and those in Example 2.The purification procedures allow for the isolation of higher sialicacid containing Epo isoforms resulting from adding additionalcarbohydrate chains.

The Epo hyperglycosylated analogs may include, in addition to newglycosylation sites, additions, deletions or substitutions of amino acidresidues which do not create new glycosylation sites and do notsubstantially alter the biological activity of the hyperglycosylatedanalog. Those individual sites or regions of Epo which may be alteredwithout affecting biological activity may be determined by examinationof the structure of the Epo-Epo receptor complex as described in Syedet. al. Nature 395, 511 (1998). Examination of the structure of theEpo-Epo receptor complex reveals those residues which interact with, orare in close proximity to, the receptor binding site of Epo and whichshould be avoided when making alterations in the Epo amino acidsequence. Alternatively, one may empirically determine those regionswhich would tolerate amino acid substitutions by alanine scanningmutagenesis (Cunningham et al. Science 244, 1081-1085 (1989). In thismethod, selected amino acid residues are individually substituted with aneutral amino acid (e.g., alanine) in order to determine the effects onbiological activity.

It is generally recognized that conservative amino acid changes areleast likely to perturb the structure and/or function of a polypeptide.Accordingly, the invention encompasses one or more conservative aminoacid changes within an Epo hyperglycosylated analog. Conservative aminoacid changes generally involve substitution of one amino acid withanother that is similar in structure and/or function (e.g., amino acidswith side chains similar in size, charge and shape). The nature of thesechanges are well known to one skilled in the art and are summarized inTable 1 below. Such conservative substitutions are shown under theheading of “Preferred substitutions”. Also contemplated are moresubstantial changes (“Exemplary substitutions”) which may also beintroduced. A skilled artisan will appreciate that initially the sitesshould be modified by substitution in a relatively conservative manner.If such substitutions result in a retention in biological activity, thenmore substantial changes (Exemplary Substitutions) may be introducedand/or other additions/deletions may be made and the resulting productsscreened.

TABLE 1 Amino Acid Substitutions Original Preferred Exemplary ResidueSubstitutions Substitutions Ala (A) Val Val; Leu; Ile Arg (R) Lys Lys;Gln; Asn Asn (N) Gln Gln; His; Lys; Arg Asp (D) Glu Glu Cys (C) Ser SerGln (Q) Asn Asn Glu (E) Asp Asp Gly (G) Pro Pro His (H) Arg Asn; Gln;Lys; Arg Ile (I) Leu Leu; Val; Met; Ala; Phe; norleucine Leu (L) Ilenorleucine; Ile; Val; Met; Ala; Phe Lys (K) Arg Arg; Gln; Asn Met (M)Leu Leu; Phe; Ile Phe (F) Leu Leu; Val; Ile; Ala Pro (P) Gly Gly Ser (S)Thr Thr Thr (T) Ser Ser Trp (W) Tyr Tyr Tyr (Y) Phe Trp; Phe; Thr; SerVal (V) Leu Ile; Leu; Met; Phe; Ala; norleucine

Also provided by the invention are deletions or additions of amino acidsin a hyperglycosylated Epo analog which do not substantially affectbiological activity. Such additions and deletions may be at theN-terminal or C-terminal of the polypeptide, or may be internal to it.In general, relatively small deletions or additions are less likely toaffect structure and/or function of Epo or a hyperglycosylated analog.In one embodiment, deletions or additions can be from 5-10 residues,alternatively from 2-5 amino acid residues, or from 1-2 residues.

The invention provides for fusion proteins comprising Epohyperglycosylated analogs and compositions thereof. In one aspect, theinvention provides for fusion proteins of Epo hyperglycosylated analogsand an immunoglobulin heavy chain constant region. Fusions may be madeat the amino terminus of an Epo hyperglycosylated analog, that is, thecarboxy terminus of an immunoglobulin heavy chain constant region isfused to the amino terminus of an Epo hyperglycosylated analog.Alternatively, it may be desirable to fuse the carboxy terminus of anEpo hyperglycosylated analog to the amino terminus of an immunoglobulinheavy chain constant region. In one aspect of the invention, theimmunoglobulin heavy chain constant region is an Fc region. Epohyperglycosylated analogs, when part of a fusion polypeptide, may be 165or 166 amino acids in length, or may have greater or fewer residues ifamino acids are added or deleted. In one embodiment, analog N47 is fusedat its C-terminus to the N-terminus of an Fc region derived from humanIgGγ1. (See Example 2.) In the present example, analog N47 includes thearginine residue at position 166. However, it is contemplated thatanalog N47 as well as other hyperglycosylated analogs of residues 1-165(lacking the C-terminal arginine residue) may also comprise the fusionpolypeptides of the invention.

The term “Fc” refers to a molecule or sequence comprising the sequenceof a non-antigen-binding portion of antibody, whether in monomeric ormultimeric form. The original immunoglobulin source of an Fc ispreferably of human origin and may be from any isotype, e.g., IgG, IgA,IgM, IgE or IgD. One method of preparation of an isolated Fc moleculeinvolves digestion of an antibody with papain to separate antigen andnon-antigen binding portions of the antibody. Another method ofpreparation of an isolated Fc molecules is production by recombinant DNAexpression followed by purification of the Fc molecules so expressed. Afull-length Fc consists of the following Ig heavy chain regions: CH1,CH2 and CH3 wherein the CH1 and CH2 regions are typically connected by aflexible hinge region. In one embodiment, an Fc has the amino acidsequence of IgG1 such as that shown in FIG. 10. The terms “Fc protein,“Fc sequence”, “Fc molecule”, “Fc region” and “Fc portion” are taken tohave the same meaning as “Fc”.

The term “Fc fragment” when used in association with Fc molecule, orfusion polypeptides thereof, refers to a peptide or polypeptide thatcomprises less than the full length amino acid sequence of an Fcmolecule. Such a fragment may arise, for example, from a truncation atthe amino terminus, a truncation at the carboxy terminus, and/or aninternal deletion of a residue(s) from the amino acid sequence. Fcfragments may result from alternative RNA splicing or from in vivoprotease activity.

The term “Fc variant” when used in association with an Fc molecule, orwith fusion polypeptides thereof, refers to a polypeptide comprising anamino acid sequence which contain one or more amino acid sequencesubstitutions, deletions, and/or additions as compared to native Fcamino acid sequences. Variants may be naturally occurring orartificially constructed. Variants of the invention may be prepared fromthe corresponding nucleic acid molecules encoding said variants, whichhave a DNA sequence that varies accordingly from the DNA sequences fornative Fc molecule.

The term “derivative” when used in association with an Fc molecule, orwith fusion polypeptides thereof, refers to Fc variants or fragmentsthereof, that have been chemically modified, as for example, by covalentattachment of one or more polymers, including, but limited to, watersoluble polymers, N-linked or O-linked carbohydrates, sugars,phosphates, and/or other such molecules. The derivatives are modified ina manner that is different from native Fc, either in the type orlocation of the molecules attached to the polypeptide. Derivativesfurther includes deletion of one or more chemical groups naturallyattached to an Fc molecule.

The term “fusion” refers to joining of different peptide or proteinsegments by genetic or chemical methods wherein the joined ends of thepeptide or protein segments may be directly adjacent to each other ormay be separated by linker or spacer moieties such as amino acidresidues or other linking groups.

An Fc, or a variant, fragment or derivative thereof, may be from an Igclass. In one embodiment, an Fc is from the IgG class, such as IgG1,IgG2, IgG3, and IgG4. In another embodiment, an Fc is from IgG1. An Fcmay also comprise amino acid residues represented by a combination ofany two or more of the Ig classes, such as residues from IgG1 and IgG2,or from IgG1, IgG2 and IgG3, and so forth. In one embodiment, an Fcregion of an Epo hyperglycosylated analog fusion protein has thesequence as set forth in FIG. 10 (SEQ ID NO:_) (see Ellison et al.,Nucleic Acids Res. 10, 4071-4079 (1982)) starting at residue 6 (that is,residues 1-5 are deleted).

In addition to naturally occurring variations in Fc regions, Fcvariants, fragments and derivatives may contain non-naturally occurringchanges in Fc which are constructed by, for example, introducingsubstitutions, additions, insertions or deletions of residues orsequences in a native or naturally occurring Fc, or by modifying the Fcportion by chemical modification and the like. In general, Fc variants,fragments and derivatives are prepared such that the increasedcirculating half-life of Fc fusions to Epo glycosylation analogs islargely retained.

Also provided by the invention are Fc variants with conservative aminoacid substitutions. Examples of conservative amino acid substitutionsare set forth hereinabove, and are also exemplified by substitution ofnon-naturally occurring amino acid residues which are typicallyincorporated by chemical peptide synthesis rather than by synthesis inbiological systems. These include peptidomimetics, and other reversed orinverted forms of amino acid moieties. Conservative modifications to theamino acid sequence of an Fc region (and the corresponding modificationsto the encoding nucleotides) are expected to produce Fc molecules (andfusion proteins comprising Epo hyperglycosylated analogs and Fc regions)which have functional and chemical characteristics similar to those ofunmodified Fc molecules and fusion proteins comprising unmodified Fcregions.

In addition to the substitutions set forth in Table I, any nativeresidue in an Fc molecule (or in an Fc region of a fusion proteincomprising an Epo hyperglycosylated analog) may also be substituted withalanine, as has been previously described for “alanine scanningmutagenesis” (Cunningham et al. Science 244, 1081-1085 (1989)).

Substantial modifications in the functional and/or chemicalcharacteristics of an Fc molecule (and in an Fc region of a fusionprotein comprising an Epo hyperglycosylated analog) may be accomplishedby selecting substitutions that differ significantly in their effect onmaintaining (a) the structure of the molecular backbone in the area ofthe substitution, for example, as a sheet or helical conformation, (b)the charge or hydrophobicity of the molecule at the target site, or (c)the bulk of the side chain. Naturally occurring residues may be dividedinto groups based on common side chain properties:

-   -   1) hydrophobic: norleucine, Met, Ala, Val, Leu, Ile;    -   2) neutral hydrophilic: Cys, Ser, Thr;    -   3) acidic: Asp, Glu;    -   4) basic: Asn, Gln, His, Lys, Arg;    -   5) residues that influence chain orientation: Gly, Pro; and    -   6) aromatic: Trp, Tyr, Phe.

Non-conservative substitutions may involve the exchange of a member ofone of these classes for a member from another class. Such substitutedresidues may be introduced into regions of an Fc molecule that arehomologous with a non-human Fc molecule, or into the non-homologousregions of the molecule.

Cysteine residues in Fc molecules can be deleted or replaced with otheramino acids to prevent formation of disulfide crosslinks. In particular,a cysteine residue at position 5 of FIG. 10 (SEQ. ID. NO. _) may besubstituted with one or more amino acids, such as alanine or serine.Alternatively, the cysteine residue at position 5 could be deleted.

An Fc fragment may be prepared by deletion of one or more amino acids atany of positions 1, 2, 3, 4 and 5 as shown in FIG. 10 (SEQ ID NO. _). Inone embodiment, the amino acid residues at positions 1-5 inclusive aredeleted. Substitutions at these positions can also be made and are within the scope of this invention.

Fc variants may also be made which show reduced binding to Fc receptorswhich trigger effector functions such as antibody dependent cellularcytotoxicity (ADCC) and activation of complement (see for example Molec.Immunol. 29, 633-639, (1992)). Such variants may include leucine atposition 20 deleted or substituted with a glutamine residue, glutamateat position 103 deleted or substituted with an alanine residue, andlysines at positions 105 and 107 deleted or substituted with alanineresidues (following the numbering as set forth in FIG. 1). One or moreof such substitutions are contemplated.

In one embodiment, Fc variants will exhibit stronger binding to the FcRnreceptor (“salvage receptor”) and a longer circulating half-lifecompared to native Fc such as that shown in FIG. 1. Example of suchvariants include amino acid substitutions at one or more of residues 33,35-42, 59, 72, 75, 77, 95-98, 101, 172-174, 215 and 220-223, wherein thesubstitution(s) confer tighter binding of an Fc variant to the FcRnreceptor. In another embodiment, Fc variants have one or moreglycosylation sites removed. N-linked glycosylation sites may be removedby deletion substitution of asparagine residues having attachedcarbohydrate chains.

Other Fc variants include one or more tyrosine residues replaced with,for example, phenyalanine residues. In addition, other variant aminoacid insertions, deletions and/or substitutions are also contemplatedand are within the scope of the present invention. Examples include Fcvariants disclosed in WO96/32478 and WO97/34630 hereby incorporated byreference. Furthermore, alterations may be in the form of altered aminoacids, such as peptidomimetics or D-amino acids.

The Fc protein may be also linked to the Epo glycosylation analogs by“linker” moieties comprising chemical groups or amino acids of varyinglengths. Such chemical linkers are well known in the art. Amino acidlinker sequences can include but are not limited to:

(a) ala-ala-ala;

(b) ala-ala-ala-ala;

(c) ala-ala-ala-ala-ala;

(d) gly-gly;

(e) gly-gly-gly;

(f) gly-gly-gly-gly-gly;

(g) gly-gly-gly-gly-gly-gly-gly;

(h) gly-pro-gly;

(i) gly-gly-pro-gly-gly; and

(j) any combination of subparts (a) through (i).

While Fc molecules are preferred as components of fusion proteins withEpo glycosylation analogs, it is also contemplated that other amino acidsequences which bind to an FcRn receptor and confer increased in vivohalf-life may also be used. Examples of such alternative molecules aredescribed in U.S. Pat. No. 5,739,277, issued Apr. 14, 1998 to Presta etal.

The term “molar amount” refers to an amount of a hyperglycosylatedanalog or rHuEpo which is based upon the molecular weight of thecorresponding erythropoietin polypeptide without glycosylation.Equivalent amounts of rHuEpo and analog refer to amounts which are equalwhen taking into account normal variations in procedure used todetermine such amounts. It is necessary to determine equivalent amountsin this manner since the molecular weight of rHuEpo and analogs willvary depending upon the number of carbohydrate chains. For rHuEpo, themolecular weight of erythropoietin polypeptide is calculated based uponamino acid residues 1-165 as shown in FIG. 1 and SEQ ID NO: 1. Forhyperglycosylated analogs, the molecular weights are adjusted dependingupon the amino acid changes in residues 1-165 of FIG. 1 and SEQ ID NO:1.

The dosing frequency for a hyperglycosylated analog will vary dependingupon the condition being treated and the target hematocrit, but ingeneral will be less than three times per week. The dosing frequencywill be about two times per week, about one time per week. The dosingfrequency may also be less than about one time per week, for exampleabout one time every two weeks (about one time per 14 days), one timeper month or one time every two months. It is understood that the dosingfrequencies actually used may vary somewhat from the frequenciesdisclosed herein due to variations in responses by different individualsto the Epo analogs; the term “about” is intended to reflect suchvariations.

As used herein, the term “therapeutically effective amount” refers to anamount of a hyperglycosylated analog (or a fusion protein comprising anEpo hyperglycosylated analog and an immunoglobulin heavy chain constantregion) which gives an increase in hematocrit to a target hematocrit, orto a target hematocrit range that provides benefit to a patient or,alternatively, maintains a patient at a target hematocrit, or within atarget hematocrit range. The amount will vary from one individual toanother and will depend upon a number of factors, including the overallphysical condition of the patient, severity and the underlying cause ofanemia and ultimate target hematocrit for the individual patient. Atarget hematocrit is typically at least about 30%, or in a range of30%-38%, preferably above 38% and more preferably 40%-45%. Generalguidelines relating to target hematocrit ranges for rHuEpo are alsofound in the EPOGEN® package insert dated Dec. 23, 1996 and are 30%-36%,or alternatively 32%-38% as stated therein. It is understood that suchtargets will vary from one individual to another such that physiciandiscretion may be appropriate in determining an actual target hematocritfor any given patient. Nonetheless, determining a target hematocrit iswell within the level of skill in the art.

A therapeutically effective amount of the present compositions may bereadily ascertained by one skilled in the art. Example 6 sets forth aclinical protocol which has as one objective to determine atherapeutically effective amount of analog N47 in both once per week andthree times per week dosing. A dose range for once per weekadministration is from about 0.075 to about 4.5 μg erythropoietinpeptide per kg per dose. A dose range for three times per weekadministration is 0.025 to 1.5 μg erythropoietin peptide per kg perdose. This dose range may be employed with other Epo hyperglycosylatedanalogs, with any adjustments in the dosing range being routine to oneskilled in the art.

A significant advantage to the present invention is the ability tocorrelate the extent of hyperglycosylation either with a dose amount orwith a dosing interval that would allow one to “tailor” an Epo analog toa given dose or dosing schedule. Based upon the increasing in vivoactivities of Epo analogs having one, two or three additionalcarbohydrate chains as shown in FIG. 3, the treating physician canselect an analog that is appropriate and convenient for the anemiccondition being treated. For example, in patients who are acutely anemicand in need of a large effective dose, or in patients which require alonger-lasting treatment, administration of a hyperglycosylated analogwith three or four or even more additional carbohydrate chains may bepreferred. For other patients who experience less severe anemia orrequire treatment for a relatively short time, an analog with one or twoadditional carbohydrate chains may be preferred. The analogs of thepresent invention provide the physician with considerable flexibility inpreventing and treating anemia that may result from a wide variety ofunderlying conditions.

The invention also provides for administration of a therapeuticallyeffective amount of iron in order to maintain increased erythropoiesisduring therapy. The amount to be given may be readily determined by oneskilled in the art based upon therapy with rHuEpo.

The present invention may be used to stimulate red blood cell productionand prevent and treat anemia. Among the conditions treatable by thepresent invention include anemia associated with a decline or loss ofkidney function (chronic renal failure), anemia associated withmyelosuppressive therapy, such as chemotherapeutic or anti-viral drugs(such as AZT), anemia associated with the progression of non-myeloidcancers, anemia associated with viral infections (such as HIV), andanemia of chronic disease. Also treatable are conditions which may leadto anemia in an otherwise healthy individual, such as an anticipatedloss of blood during surgery. In general, any condition treatable withrHuEpo may also be treated with the Epo hyperglycosylated analogs of theinvention.

The invention also provides for pharmaceutical compositions comprising atherapeutically effective amount of an Epo hyperglycosylated analog,together with a pharmaceutically acceptable diluent, carrier,solubilizer, emulsifier, preservative and/or adjuvant. The inventionalso provides for a pharmaceutical composition comprising atherapeutically effective amount of a fusion protein comprising an Epohyperglycosylated analog and an immunoglobulin heavy chain constantregion together with a pharmaceutically acceptable diluent, carrier,solubilizer, emulsifier, preservative and/or adjuvant. The compositionwill be suitable for a dosing schedule of less than three times perweek. The composition may be in a liquid or lyophilized form andcomprises a diluent (Tris, citrate, acetate or phosphate buffers) havingvarious pH values and ionic strengths, solubilizer such as Tween orPolysorbate, carriers such as human serum albumin or gelatin,preservatives such as thimerosal, parabens, benzylalconium chloride orbenzyl alcohol, antioxidants such as ascorbic acid or sodiummetabisulfite, and other components such as lysine or glycine. Selectionof a particular composition will depend upon a number of factors,including the condition being treated, the route of administration andthe pharmacokinetic parameters desired. A more extensive survey ofcomponents suitable for pharmaceutical compositions is found inRemington's Pharmaceutical Sciences, 18th ed. A. R. Gennaro, ed. Mack,Easton, Pa. (1980). In a preferred embodiment, the Epo glycosylationanalogs of the invention are formulated in liquid form in an isotonicsodium chloride/sodium citrate buffered solution containing humanalbumin, and optionally containing benzyl alcohol as a preservative. Thecompositions preferably contain analogs having one, two, three, four, ormore additional carbohydrate chains.

Compositions of the invention are preferably administered by injection,either subcutaneous or intravenous. The route of administrationeventually chosen will depend upon a number of factors and may beascertained by one skilled in the art.

The following examples are offered to more fully illustrate theinvention, but are not to be construed as limiting the scope thereof.

EXAMPLE 1 Construction of Hyperglycosylated Epo Analogs

Construction of cDNAs encoding Hyperglycosylated Epo Analogs

Epo analogs were made by in vitro mutagenesis using several differentmethods. Analogs N49 and N50 were constructed as described inWO94/09257. Analogs were also constructed by variations of overlap PCR(polymerase chain reaction) methods. The basic procedure included twosuccessive steps. In the first step, two reactions (PCR1 and PCR2) wereperformed on Epo or Epo analog template DNA using a total of fouroligonucleotides: a 5′ (forward) primer, a reverse mutagenic primer, aforward mutagenic primer (usually complementary to the reverse mutagenicprimer) and a 3′ (reverse) primer. The mutagenic primers contained thedesired nucleotide changes as well as 6-14 exact match nucleotides oneach side of these changes. PCR1 used the 5′ (forward) primer and thereverse mutagenic primer. PCR2 used the 3′ (reverse) primer and theforward mutagenic primer. The amplified DNA fragments were separated byagarose gel electrophoresis. Small pieces of agarose containing DNAfragments of the correct size were excised from the gel. The DNAfragments from PCR1 and PCR2 were combined together and a third PCRreaction was performed using only the 5′ forward and 3′ reverse primers.Thus, a full length DNA segment containing the desired mutations wasamplified. In several cases, two or three mutations were combined byintroducing a new substitution into DNA already containing a change,using the same PCR process. To construct these multiple glycosylationsite analogs, single double or triple site analogs (produced asdescribed above) were used as PCR template, and an additionalglycosylation site was introduced by site directed mutagenesis with theappropriate primers.

The Epo analogs N51, N52 and N53 were constructed by the overlap PCR(polymerase chain reaction) method 1. One additional N-glycosylationsite was introduced in each case. N56 added a glycosylation site (N114T116) to native sequence HuEpo by using pDSRα2 Epo as PCR template, N51added an O-linked glycosylation site (Thr125) to N47 Epo by using pDSRα2Epo N47 template (Asn30, Thr32, Val87, Asn88, Thr90) and analog N59added a glycosylation site (Asn53) to analog N47 using pDSRα2 EpoN47template.

Polymerase chain reactions for method 1 were performed using a protocoladapted from Cheng et. al., (Proc. Natl. Acad. Sci. USA 91, 5695(1994)). The 3′ (reverse) primer contained sequences that introduced astop codon followed by a Xba I restriction site:

ATCTAGAAGTTGCTCTCTGGACAGTTCCT. (SEQ ID NO: 2) The 5′ forward reactionprimer: GAAGCTTGCGCCACCATGGGGGTGCACGAATG (SEQ ID NO: 3)had an Hind III restriction site followed by a Kozak sequence upstreamof the Epo initiator codon (ATG). The typical PCR reaction mixcontained: 4 μl each of forward and reverse primers (5 pmol/μl), 1 μltemplate (25 ng), 10 μl of 5× LP buffer (100 mM Tricine pH 8.7/25%glycerol/425 mM KOAc), 10 μl dNTP stock (1 mM each of dATP, dTTP, dCTP,dGTP), 0.8 μl rtTh polymerase (Perkin Elmer; 2.5 U/μl), and 2 μl Ventpolymerase (NEB; 0.01 U/μl after 1:100 fresh dilution in 1× LP buffer).H₂O was added to bring the final volume to 50 μl. All the componentswere added together in the order shown and the PCR was started when thetemperature during the first cycle was above 60° C. by adding 1 μl of 50mM MgOAc. Typical reaction conditions were: 2 cycles of 94° C., 10sec/50° C., 1 min./68° C., 5 min. followed by 25 cycles of 94° C., 10sec/55° C., 1 min./68° C., 5 min. The amplified fragments were separatedby agarose gel electrophoresis and the correct sized DNA fragment waspurified using a Geneclean™ kit and procedures supplied by themanufacturer (Bio 101, Inc.). The purified DNA was digested with HindIII and Xba I, then it was purified again using the Geneclean™ kit. Thefragment was then ligated into Hind III and Xba I cut pDSRα2 vector.Ligated DNA was precipitated with 2 volumes of ethanol in 0.3M NaOAc pH5.2 in the presence of carrier tRNA and transformed into E. coli. Epoanalogs were screened by restriction digest on mini DNA preps. Plasmidsfrom positive clones were then prepared and the insert was sequenced toconfirm the presence of the desired mutations and to ensure that noadditional amino acid changes were introduced.

Analogs N54 to N61 were constructed using overlap PCR strategy method 2.The 3′ (reverse) primer contained sequences that introduced a stop codonfollowed by a XbaI restriction site:

GATCCTCTAGAGTTGCTCTCTGGACAG. (SEQ ID NO: 4) The 5′ forward reactionprimer: CAACAAGCTTGCGCCGCCATGGGGG (SEQ ID NO: 5)had a HindIII restriction site followed by a Kozak sequence upstream ofthe Epo initiator codon (ATG). A high fidelity PCR strategy wasperformed using Perkin Elmer UlTma DNA Polymerase and accompanyingreagents; 10 μl 10×PCR buffer, 3 μl 1 mM dNTPs, 5 pmol of each primer,and water in a final volume of 100 μl. 0.5 units of UlTma polymerase wasadded after the PCR mixture reached 94° C. PCR reactions were thencarried out for 5 cycles at 94° C. for 30 seconds, 50° C. for 30seconds, and 72° C. for 90 seconds. A subsequent 25 cycles wereperformed at 94° C. for 30 seconds, and 72° C. for 90 seconds. Productbands of the correct sizes were excised from an agarose gel followingelectrophoresis.

The resulting PCR products for each analog were cleaned using the Qiagengel extraction kit. The purified DNA was digested in a 100 μlrestriction digest with HindIII and XbaI restriction enzymes (BoehringerMannheim) at 37° C. for 1 hour. The digests were again gel purified andthe digested fragment was then ligated into HindIII and XbaI digestedpDSRα2 vector.

Ligated DNA was precipitated with 2 volumes of ethanol in 0.3M NaOAc pH5.2 in the presence of carrier tRNA and transformed into E. coli. Epohyperglycosylated analogs were initially screened by colony PCR toidentify clones containing the correctly sized and type of DNA insert.With this procedure, cells containing plasmids were placed into PCRtubes in the presence of Epo forward and reverse primers. The mixturewas then subjected to PCR using the reaction conditions described above.Plasmids from positive clones were then prepared and the Epo analoginsert was sequenced to confirm the presence of the desired mutationsand to ensure that no additional amino acid changes were introduced.

TABLE 1 ERYTHROPOIETIN ANALOGS HAVING SITES FOR N-LINKED CARBOHYDRATECHAINS Amino Acid Sequence Analog Substitution Changes N49 Lys,Met→Asn52, Thr54 AAG, ATG→AAT, ACC N50 Arg, Glu→Asn53, Thr55 AGG,GAG→AAT, ACG N51 Ala, His, Pro, Trp, Pro, Ala → GCT, CAC, CCG, TGG, CCC,N30, T32, V87, N88, T90 T125 GCC→AAT, ACG, GTG, AAT, ACC, ACC N52 Ala,Lys→Asn114, Thr116 GCC, AAG→AAC, ACG           → N53 Ala, His, Arg, GluPro, Trp, Pro → GCT, CAC, AGG, GAG, CCG, N30, T32, N53, T55, V87, N88,T90 TGG, CCC→AAT, ACG, AAT, ACG, GTG, AAT, ACC N54 Glu, Gly → Asn55,Thr57 GAG, GGG→AAT, ACT N55 Gln, Pro, Trp → Asn86, Val87, Thr88 CAG,CCG, TGG→ACC, GTG, ACG N56 Pro, Trp, Pro→ Ala87, Asn88, Thr90 CCG, TGG,CCC→GCG, AAT, ACC N57 Pro, Trp, Pro→ Val87, Asn88, Ser90 CCG, TGG,CCC→ GTG, AAT, ACG N58 Pro, Trp, Glu, Pro→ CCG, TGG, GAG, CCC→ Val87,Asn88, Gly89, Thr90 GTG, AAT, GGG, ACC N59 Ala, His, Arg, Glu → GCT, CACAGG GAG→ Asn30, Thr32, Asn53 Asn55 AAT, ACG, AAT, ACG N60 Ala, His, Ala,Lys → GCT, CAC, GCC, AAG→ Asn30, Thr32, Asn114, Thr116 AAT, ACG, AAC,ACG N61 A, H, R, E, P, W, P, A, K → GCT, CAC, ACG, GAG, CCG, N30, T32,N53, T55, V87, TGG, CCC, GCC, AAG→AAT, ACG, N88, T90, N114, T115 AAT,ACG, GTG, AAT, ACC, AAC, ACG

Analysis of Carbohydrate Addition

The constructs for the hyperglycosylated Epo analogs which were insertedinto the expression vector pDSRα2 were transfected into COS cells.Supernatants from the transfected COS cells were analyzed by westernblot to determine whether the expressed and secreted Epo analogcontained additional carbohydrate. Samples were loaded directly intowells of SDS-PAGE gels then analyzed by immunoblot using the monoclonalantibody, 9G8A (Elliott et al (1996) Blood 87:p 2714). Mobilities ofanalog samples were compared to that of samples containing rHuEpo. FIG.1 shows decreased mobility of analogs N53 and N61 compared to analogs N4(four carbohydrate chains) and N47 (five carbohydrate chains). Themobility is consistent with the presence of six carbohydrate chains foranalog N53 and seven carbohydrate chains for analog N61. Data for allhyperglycosylated analogs are shown in Table 2.

In Vitro Bioassays

Media conditioned by COS or CHO cells expressing rHuEpo or analogs wereassayed for stimulation of 3H-thymidine uptake by UT7-Epo cells (Komatsuet al., Blood 82, 456). UT7-Epo cells are responsive to Epo and expresshuman Epo receptors on their cell surface. UT7-Epo cells were grown inGrowth medium (1× Iscove's Modified Dulbecco's Medium with L-glutamine,25 mM HEPES buffer, and 3024 mg/L sodium bicarbonate, but without eitheralpha-thioglycerol or beta-mercaptoethanol (GIBCO)/10% v/v Fetal BovineSerum/1% v/v L-glutamine-Penicillin-Streptomycin solution (IrvineScientific)/1 Unit/mL rHuEpo) to approximately 3×10⁵ cells/mL. Cellswere collected by centrifugation (approx. 500×G) washed twice withphosphate buffered saline and resuspended at 5×10⁴ cells/mL in Assaymedium (1×RPMI Medium 1640 without L-glutamine (Gibco)/1% L-glutamine/4%fetal bovine serum). Test samples or Epo standard (rHuEpo), 100 uLdiluted in assay medium at least 5-fold, were added to wells in a 96well microtiter plate. 50 μL of suspended cells were then added (5000cells/well) and plates were incubated in a humidified incubator at 37°C. and 5% CO₂. After 72 hours, 50 uL methyl-³H-Thymidine (1 mCi/mL; 20Ci/mMole) diluted 1:100 in assay medium was added. Cells were incubatedfor an additional 4 hours at 37° C. 5% CO₂. Labeled cells were harvestedonto glass fiber filtermats, washed with deionized water followed by2-propanol, dried and counted. Activity was determined by comparing theresponse determined for each analog to that of the rHuEpo standard. Thespecific biological activity was then determined by dividing in vitroactivity by the concentration of each analog as determined byimmunoassay (Elliott et al (1996) Blood 87:p 2714). The results areshown in Table 2.

TABLE 2 Number of N-linked ANALOG Carbohydrate Chains In VitroActivity** rHuEpo 3 +++ N49 4 +++ N50 4 +++ N51  5* +++ N52 3-4 +++ N536 ++ N54 4 NT N55 4 +++ N56 4 +++ N57 3-4 +++ N58 4 +++ N59 5 ++ N60 4-5+++ N61 6-7 NT *contains 1-2 O-linked chains **In vitro activity isrelative to rHuEpo activity +++ activity equivalent to rHuEpo ++activity is 25-75% of rHuEpo NT Not Tested

Epo analogs N62-N69 were made by overlap PCR (polymerase chain reaction)methods. The basic procedure included two successive steps. In the firststep, two reactions (PCR1 and PCR2) were performed on Epo or Epo analogtemplate DNA using a total of four oligonucleotides: a 5′ (forward)primer, a reverse mutagenic primer, a forward mutagenic primercomplementary to the reverse mutagenic primer and a 3′ (reverse) primer.The mutagenic primers contained the desired nucleotide changes as wellas 6-14 exact match nucleotides on each side of these changes. PCR1 usedthe 5′ (forward) primer and the reverse mutagenic primer. PCR2 used the3′ (reverse) primer and the forward mutagenic primer. The amplified DNAfragments were separated by agarose gel electrophoresis and DNAfragments of the correct size were excised and eluted from the gel. TheDNA fragments from PCR1 and PCR2 were combined together and a third PCRreaction was performed using only the 5′ forward and 3′ reverse primers.For some analogs, three PCR reactions were required to generate thedesired sequence. These were carried out as above, with a second pair ofmutagenic primers being used to generate the third product. Again, theamplified DNA fragments were gel purified and combined in a finalreaction containing only the 5′ forward and 3′ reverse primers. In eachcase, a full length DNA segment containing the desired mutations wasamplified.

N62 added two glycosylation sites (N30 T32 N55 T57) to native sequenceHuEpo by using pDSRα2 Epo N4 (N30 T32) as PCR template. N63 added threeglycosylation sites (N30 T32 N55 T57 V87 N88 T90) to native sequenceHuEpo by using pDSRα2 Epo N4 (N30 T32) and pDSRα2 Epo N47 (N30 T32 N55T57) as PCR templates. N64 added three glycosylation sites (N30 T32 N55T57 N114 T116) to native sequence HuEpo by using pDSRα2 Epo N4 (N30 T32)and pDSRα2 Epo N60 as PCR templates. N65 added three glycosylation sites(N30 T32 V87 N88 T90 N114 T116) to native sequence HuEpo by using pDSRα2Epo N4 (N30 T32) and pDSRα2 Epo N60 as PCR templates. N66 added fourglycosylation sites (N30 T32 N55 T57 V87 N88 T90 N114 T116) to nativesequence HuEpo by using pDSRα2 Epo N4 (N30 T32) and pDSRα2 Epo N60 asPCR templates. N67 added an O-linked glycosylation site (P124 T125 T126) to N64 Epo. N68 added an O-linked glycosylation site (P124 T125 T126) to N65 Epo. N69 added an O-linked glycosylation site (P124 T125 T126) to N66 Epo.

For each analog, the same outside primers were used. The 3′ (reverse)primer contained sequences that introduced a stop codon followed by aSal I restriction site:

AGGTGGACAGTCGACATTATCTGTCCCCTGTC. (SEQ ID NO:  ) The 5′ forward reactionprimer: AACAAGCTTCTAGACCACCATGGGGGTG (SEQ ID NO:  )had a Hind III restriction site followed by a Kozak sequence upstream ofthe Epo initiator codon (ATG). Mutagenic primers were as follows:

N30 T32 mutagenic forward primer (SEQ ID NO:  ) ACG ACG GGC TGT AAT GAAACG TGC AGC TTG N30 T32 mutagenic reverse primer (SEQ ID NO:  ) CAA GCTGCA CGT TTC ATT ACA GCC CGT CGT G N55 T57 mutagenic forward primer (SEQID NO:  ) GCC TGG AAG AGG ATG AAT GTC ACGCAG CAG GCC GTA GAA N55 T57mutagenic reverse primer (SEQ ID NO:  ) TTC TAC GGC CTG CTG CGT GACATTCAT CCT CTT CCA GGC A V87 N88 T90 mutagenic forward primer (SEQ IDNO:  ) TCT TCC CAG GTG AAT GAG ACC CTG CAG CTG V87 N88 T90 mutagenicreverse primer (SEQ ID NO:  ) CAG CTG CAG GGT CTC ATT CAC CTG GGA AGAGTT G P124 T125 T126 mutagenic forward primer (SEQ ID NO:  ) CCA GAT CCGACC ACA GCT GCT CCA P124 T125 T126 mutagenic reverse primer (SEQ IDNO:  ) TGG AGC AGC TGT GGT CGG ATC TGG AThe N114 T116 changes were introduced using a template containing theappropriate mutations, so no mutagenic primers were required to generatethis site.The typical PCR1 reaction mix contained: 2.5 μl each of forward andmutagenic reverse primers (10 pmol/μl), 1 μl template (25 ng), 10 μl of10× Taq Extend buffer (Stratagene), 2 μl dNTP stock (10 mM each of DATP,dTTP, dCTP, dGTP), 0.5 μl Taq polymerase (BMB), and 0.5 μl Taq Extend(Stratagene). H₂O was added to bring the final volume to 100 μl. Typicalreaction conditions were: 1 cycle of 94° C., 5 min./55° C., 1 min./68°C., 1 min. followed by 25 cycles of 94° C., 1 min./55° C., 1 min./68°C., 1 min. The typical PCR2 reaction was identical to that described forPCR 1, except that the reverse and mutagenic forward primers were used.Where a third initial reaction was required, the reaction containedmutagenic forward and mutagenic reverse primers. The amplified fragmentswere separated by agarose gel electrophoresis and the correct sized DNAfragment was purified using a Gel Extraction kit and procedures suppliedby the manufacturer (Qiagen). Complementary fragments were then combinedin a third PCR reaction using only the outside forward and reverseprimers. The amplified fragments were separated by agarose gelelectrophoresis and purified from the gel as described above. Thepurified DNA was digested with Hind III and Sal I, then it was again gelpurified. The fragment was then ligated into Hind III and Sal I cutpDSRα19 vector. Ligated DNA transformed by electroporation into E. coli.Epo hyperglycosylated analogs were initially screened by colony PCR toidentify clones containing the correctly sized DNA insert. Plasmid DNAfrom selected clones was then prepared and the insert was sequenced toconfirm the presence of the desired mutations and to ensure that noadditional amino acid changes were introduced.

TABLE 3 ERYTHROPOIETIN ANALOGS HAVING SITES FOR N-LINKED CARBOHYDRATECHAINS Amino Acid Sequence Analog Substitution Changes N62 Ala, His,Glu, Gly → GCT, CAC, GAG, GGG→ Asn30, Thr32, Asn55 Thr57 AAT, ACG, AAT,ACT N63 A, H, E, G, P, W, P→ GCT, CAC, GAG, GGG, CCG, TGG, N30, T32,N55, T57, V87, N88, T90 CCC→ AAT, ACG, AAT, ACT GTG, AAT, ACC N64 A, H,E, G, A, K→ GCT, CAC, GAG, GGG, GCC, AAG→ N30, T32, N55, T57, N114 T116AAT, ACG, AAT, ACT, AAC, ACG N65 A, H, P, W, P, A, K→ GCT, CAC, CCG,TGG, CCC, GCC, N30, T32, V87, N88, T90, N114, T116 AAG→ AAT, ACG, GTG,AAT, ACC, AAC, ACG N66 A, H, E, G, P, W, P, A, K→ GCT, CAC, GAG, GGG,CCG, TGG, N30, T32, N55, T57, V87, N88, T90, CCC, GCC, AAG→ N114, T116AAT, ACG, AAT, ACT GTG, AAT, ACC, AAC, ACG N67 A, H, E, G, P, W, P, A,A, S→ GCT, CAC, GAG, GGG, CCG, TGG, N30, T32, N55, T57, V87, N88, T90,CCC, GCG, GCC, TCA→ P124, T125, T126 AAT, ACG, AAT, ACT GTG, AAT, ACC,CCG ACC ACA N68 A, H, E, G, A, K, A, A, S→ GCT, CAC, GAG, GGG, GCC, AAG,N30, T32, N55, T57, N114 T116, P124, GCG, GCC, TCA→ T125, T126 AAT, ACG,AAT, ACT, AAC, ACG, CCG, ACC, ACA N69 A, H, E, G, P, W, P, A, K, A, A,S→ GCT, CAC, GAG, GGG, CCC, TGG, N30, T32, N55, T57, V87, N88, T90, CCC,GCC, AAG, GCG, GCC, TCA→ N114, T116, P124, T125, T126 AAT, ACG, AAT, ACTGTG, AAT, ACC, AAC, ACG, CCG, ACC, ACA N70 Ala, His, Pro, Trp, Pro →GCT, CAC, CCG, TGG, CCC→AAT, N30, T32, V87, N88, T90, IgG1 fusion ACG,GTG, AAT, ACCConstruction of cDNA Encoding Hyperglycosylated Epo Analog FusionPolypeptide

Epo analog N70 was also made by overlap PCR. Plasmid DSRα2 containingthe cDNA sequence encoding analog N47 (N30 T32 V87 N88 T90) and plasmidpAMG21 (ATCC accession no. 98113) containing cDNA encoding an Fc regionwere used as templates for the polymerase chain reactions. The Fcportion of human immunoglobulin IgG1 heavy chain from residue 104 of thehinge domain (Asp-104) to the carboxyl terminus (Ellison et al., supra,see also FIG. 10 starting at aspartic acid residue at position 6), wasgenerated by PCR amplification of a human spleen cDNA library(Clontech). Overlapping PCR products were generated in two reactionsusing the following oligonucleotide primers

5′ forward reaction primer 2343-85 (Epo specific) (SEQ ID NO:  ) AAC AAGCTT CTA GAC CAC CAT GGG GGT G 3′ reverse reaction primer 2343-87(homology to both Epo and Fc): (SEQ ID NO:  ) AGG TGG ACA TGT GTG AGTTTT GTC TCT GTC CCC TCT CCT GCA GGC CTC C 5′ forward reaction primer2343-86 (homology to both Epo and Fc): (SEQ ID NO:  ) GAG GCC TGC AGGACA GGG GAC AGA GAC AAA ACT CAC ACA TGT CCA CCT 3′ reverse reactionprimer 2343-88 (specific to Fc) (SEQ ID NO:  ) TGG ACA GTC GAC ATT ATTTAC CCG GAG ACA GGG AGA GGC TCT TCT GCPCR1 contained 2.5 μl each of forward (2343-85) and reverse (2343-87)primers (10 pmol/μl), while PCR2 contained 2.5 μl each of forward(2343-86) and reverse (2343-88) primers (10 pmol/μl). Conditions were asdescribed above. The resulting amplified products contained a region ofoverlap (48 nucleotides) encoding the last 8 amino acids of Epo and thefirst 8 amino acids of Fc. The complementary fragments were gel purifiedand combined in a third PCR reaction using only the outside forward andreverse primers. The amplified fragment was separated by agarose gelelectrophoresis and purified from the gel as described above. Thepurified DNA was digested with Hind III and Sal I, then it was again gelpurified. The fragment was then ligated into Hind III and Sal I cutpDSRα19 vector. Ligated DNA transformed by electroporation into E. coli.Transformants were initially screened by colony PCR to identify clonescontaining the correctly sized DNA insert. Plasmid DNA from selectedclones was then prepared and the insert was sequenced to confirm thesequence of the fusion protein and to ensure that no additional aminoacid changes were introduced.

Analysis of Carbohydrate Addition

The constructs for the hyperglycosylated Epo analogs N62 to N69 andfusion protein (analog N70) were inserted into the expression vectorpDSRα19 and transfected into CHO cells. Supernatants from thetransfected CHO cells are analyzed by western blot to determine whetherthe expressed and secreted Epo analogs contained additional carbohydrateusing procedures described above for analogs N49 to N62.

In Vitro Bioassays

In vitro assays for analogs N62 to N70 expressed in CHO transfectedcells are performed as described above for analogs N49 to N61.

EXAMPLE 2 Preparation of Recombinant Human Erythropoietin andHyperglycosylated Erythropoietin Analogs

Recombinant human erythropoietin (rHuEpo) used for the experimentsdescribed herein was expressed by Chinese hamster ovary (CHO) cellstransfected with a recombinant plasmid carrying the human erythropoietingene. The recombinant product was recovered from the conditioned mediumand purified essentially as described by Lai et al. supra. The resultingrHuEpo preparation has predominantly isoforms of 9 to 14 sialic acids asdetermined by isoelectric focusing.

Recombinant hyperglycosylated erythropoietin analogs were expressed inCHO cells transfected with a recombinant plasmid carrying the Epo analoggene as described WO91/05867 and WO94/09257 hereby incorporated byreference. The hyperglycosylated analogs were purified from culturesupernatants as described below.

Concentration and Diafiltration of Conditioned Media

Conditioned medium (serum free) from three successive harvests (5-8 dayseach) of the transfected CHO cell line was collected, filtered through a0.45 μm filter, concentrated about thirty fold, and diafiltered into 10mM Tris, 20 μM CuSO₄, pH 7.0 using a tangential-flow ultrafiltrationsystem (Millipore) with a 10,000 molecular weight cutoff membrane. Thedialfiltered media (DFM) was filtered (0.45 μm) a second time and storedat −20° C. until used for purification.

Purification

All procedures were carried out at 2 to 8° C.

Anion-Exchange Chromatography (1Q)

The clarified DFM was applied to a Q-Sepharose Fast Flow column(Pharmacia, 6 cm×18 cm) equilibrated in 10 mM bis Tris propane (BTP), pH7.0 and washed with two column volumes of 10 mM BTP to elute allnon-binding species. The following gradients were run depending uponwhether the hyperglycosylated analog had four, five or six N-linkedcarbohydrate chains. All buffers used at this stage contain 1 mMglycine, 20 μM CuSO₄, 6 M urea, 5 μg/mL leupeptin and 1 μg/mL pepstatin.For analogs with four N-linked carbohydrate chains, the gradient was 10mM acetic acid, 0.1 mM NaCl to 500 mM acetic acid, 5 mM NaCl over 49column volumes with a two column volume hold at high salt conditions.For analogs with five N-linked carbohydrate chains, the gradient was 0.7M acetic acid, 7 mM NaCl to 1.0 M acetic acid, 12 mM NaCl over 30 columnvolumes with a two column volume hold at high salt conditions. Foranalogs with six N-linked carbohydrate chains, the gradient was 1.0 Macetic acid, 10 mM NaCl to 1.5 M acetic acid, 20 mM NaCl over 50 columnvolumes with a two column volume hold at high salt conditions. Followingthe gradient, the column was washed with two column volumes of 10 mMBTP, pH 7.0 and the high isoform fraction was eluted with 0.6 M NaCl,100 mM BTP, pH 7.0.

Reversed Phase Chromatography (C4)

The high salt strip from the Q-Sepharose column (1Q) was applied to aVydac C4 reversed phase column (30μ particles, 4 cm×18 cm) equilibratedin 20% ethanol, 10 mM BTP, pH 7.0 and eluted from the column with athirty column volume gradient to 94% ethanol buffered in 10 mM BTP, pH7.0. The pooled product peak, eluting in approximately 60% ethanol, wasdiluted with four volumes of 10 mM BTP, pH 7.0 to minimize possibilityof aggregation in the presence of ethanol.

Anion-Exchange Chromatography (2Q)

The diluted eluate from the reversed phase column was applied to asecond Q-Sepharose Fast Flow (Pharmacia, 3 cm×9 cm) column equilibratedwith 10 mM BTP, pH 7.0. The column was washed with equilibration buffer,and the hyperglycosylated Epo analog was eluted with 0.6 M sodiumchloride, 20 mM sodium citrate, pH 6.0.

The purified protein was exchanged into 20 mM NaPO₄, pH 6.0, 140 mM NaClvia centricon (10,000 molecular weight cutoff), followed by passagethrough a 0.2 μm filter and storage at 2-8° C.

EXAMPLE 3 In Vivo Bioactivity of rHuEpo and rHuEpo Analogs ContainingFour, Five and Six N-Linked Carbohydrate Chains

The in vivo activity of Epo analogs containing four, five and sixN-linked carbohydrate chains was compared with that of rHuEpo in theexhypoxic polycythemic mouse bioassay. This assay quantifies theincorporation of ⁵⁹Fe into newly synthesized red blood cells as ameasure of the increase in erythropoiesis in mice in response to anexogenously-administered test sample. The assay, performed as describedbelow, is a modification of the method of Cotes and Bangham (Nature 191,1065 (1961)).

In this assay, female BDF₁ mice are first preconditioned by exposure tolow oxygen conditions in a hypobaric chamber (0.4-0.5 atm.) forapproximately 18 hours a day for 14 days. To compensate for the lowoxygen conditions the mice respond by stimulating erythropoiesis toincrease the number of red blood cells and thereby the relativeoxygen-carrying capacity. After completion of the final hypobaricexposure, the mice are allowed to remain at ambient pressure forapproximately 72 hours prior to the administration of test samples byintraperitoneal injection. At ambient pressure the mice are relativelypolycythemic and respond by decreasing endogenous erythropoietinproduction and the rate of erythropoiesis. Five days after sampleadministration, 0.2-0.3 μCi of ⁵⁹FeCl₃ in 0.2 mL is injectedintravenously into the tail vein. Forty-eight hours later, the animalsare sacrificed and the increase in erythropoiesis produced by the testsamples is determined by measuring the amount of ⁵⁹Fe incorporated in a0.5 mL sample of whole blood.

An example of the results obtained when rHuEpo and five different Epoanalogs, containing four, five or six N-linked carbohydrate chains weretested in this assay is shown in FIG. 3. Each sample was assayed at sixor seven different dilutions within an appropriate concentration range.All samples were diluted in phosphate-buffered saline containing 0.5%bovine serum albumin, and 0.4 mL of each dilution was administered tofive preconditioned mice. Forty-eight hours after the administration of⁵⁹Fe, the amount incorporated in 0.5 mL of blood was measured by gammacounting. The results for each of the samples are plotted as the percent⁵⁹Fe incorporated versus the log of the administered dose.

As shown in FIG. 3, all five of the hyperglycosylated Epo analogs testedin this assay were more potent than rHuEpo. In addition, the potency ofeach analog was directly dependent on the number of N-linkedcarbohydrate chains, with those analogs having an increased number ofcarbohydrate chains having the greater activity. Thus, analog N53, whichcontains six N-linked carbohydrate chains, was the most potent analog.Analog N47, which contains five N-linked carbohydrate chains, was inturn, more potent than those analogs containing four N-linked chains.The potencies of the three analogs containing four N-linked carbohydratechains (N4, N18 and N50) were approximately equal to each other andgreater than that of rHuEpo.

In this experiment, the doses of rHuEpo and analogs containing four,five or six N-linked carbohydrate chains required to produce 40% ⁵⁹Feincorporation were 10,700 ng, 640 ng, 140 ng and 38 ng, respectively.Based on the amount of material required to produce this level oferythropoiesis, Epo analogs containing four, five, or six N-linkedcarbohydrate chains are 17-fold, 77-fold and 280-fold more potent thanrHuEpo.

EXAMPLE 4 IV Pharmacokinetics of rHuEpo and Epo Analog N47 in Rats andBeagle Dogs

Two separate studies in rats and dogs were performed to compare thepharmacokinetic parameters of Epo N47 analog and rHuEpo.

In the rat studies, 1 μCi (˜0.1 μg of peptide/kg) of either ¹²⁵I-Epo N47analog, or ¹²⁵I-recombinant human erythropoietin (Amersham) was injectedintravenously into a surgically implanted carotid cannula in normal maleSprague-Dawley rats weighing between 314-363 g. At various time pointsafter administration, 0.3 mL of blood was collected and serum wasprepared by centrifugation. The level of ¹²⁵I-rHuEpo or ¹²⁵I Epo N47analog in 0.1 mL of each serum sample was then determined following anovernight 4° C. incubation with 90% ethanol. The ethanol-precipitatedprotein in each serum sample was collected by centrifugation and theradioactivity was counted in a gamma counter. The resulting serumconcentration vs time pharmacokinetic curves are shown in FIG. 4. Eachpoint represents a group mean of five rats in the N47 analog group andsix rats in the rHuEpo group. The pharmacokinetic parameters weredetermined for each rat using PCNONLIN 4.0 nonlinear regression analysis(Statistical Consultants, 1992) and the results for each group wereaveraged. The results are shown in Table 3.

TABLE 3 Comparison of IV Pharmacokinetic Parameters of N47 and r-HuEpoin Rats Half-life Serum Sample α β V_(d) Clearance Test (hours) (hours)(mL/kg) (mL/kg-hr) N47 (n = 5 rats) 0.57 ± 0.49 6.9 ± 0.3 33 ± 5  4.8 ±1.2 r-HuEpo (n = 6 rats) 0.18 ± 0.03 2.5 ± 0.2 36 ± 6 17.7 ± 3.4 a Theresults are presented as the group average ± SD for five rats in the N47group and six rats in the r-HuEpo group.

In the dog studies, normal Beagle dogs weighing between 7.8-9.5 kgreceived an intravenous bolus injection of ˜29 μCi of either ¹²⁵I-rHuEpoor ¹²⁵I-N47 (˜0.1 μg peptide/kg) into the cephalic vein. At various timepoints through 24 hours post-administration, approximately 1 to 2 mL ofblood was collected and serum prepared. The concentration of ¹²⁵I-rHuEpoand ¹²⁵I-N47 in 0.1 mL serum was determined and pharmacokineticparameters were calculated as described above. The serum concentrationvs time pharmacokinetic curves for the dog studies are shown in FIG. 5.The time points are the group means of two animals in each group. Thepharmacokinetic parameters are summarized in Table 4.

TABLE 4 Comparison of IV Pharmacokinetic Parameters of N47 and r-HuEpoin Dogs Half-life Serum Sample α β V_(d) Clearance Test (hours) (hours)(mL/kg) (mL/kg-hr) N47 0.34 25.0 55.9 2.4 r-HuEpo 0.40 7.2 60.8 8.4 aThe results presented are the average parameters for the two dogs ineach group.

In both the rat and dog studies, rHuEpo and Epo N47 analog exhibited abiphasic serum clearance. Clearance in rats was about 3.7-fold fasterfor rHuEpo than for Epo N47 analog and the β-half-life was about2.8-fold longer for Epo N47 analog than for rHuEpo. The pharmacokineticparameters in the dog studies were generally consistent with thoseobserved in rat. In dogs, the clearance of rHuEpo was 3.5-fold fasterthan for Epo N47 analog and the β-half-life was 3.5-fold longer for EpoN47 analog compared with that for rHuEpo.

EXAMPLE 5 Dose Response of Hematocrit after Administration of rHuEpo andEpo Analog N47 Hematocrit Dose Response Studies at Three Times Per Week(TIW)

The in vivo biological effects of rHuEpo and Epo analog N47 in normalmice were compared after administering a range of doses by eitherintraperitoneal or intravenous injection three times per week for up tosix weeks. Hematocrit determinations were performed twice weekly byretro-orbital bleed.

Normal CD1 mice weighing approximately 30 g (10-13 mice per group) wereinjected intraperitoneally three times per week for a total of six weekswith either rHuEpo (over the dose range of 0.625-10 μg peptide/kg/dose),Epo N47 analog (over the dose range of 0.156-1.25 μg peptide/kg/dose) orvehicle control. The vehicle control and diluent for the various rHuEpoand Epo N47 analog dosing preparations was phosphate-buffered saline(PBS), containing 0.025% mouse serum albumin. The hematocrits of allmice were determined at baseline and twice weekly thereafter byretro-orbital bleeds. At the conclusion of the experiment, serum fromall animals was collected and assayed for antibodies to the injectedproduct by a solution radioimmunoprecipitation assay. Hematocrit datafrom animals judged to be negative for neutralizing antibodies were usedfor subsequent analysis.

As shown in FIG. 6 both rHuEpo and Epo N47 analog produce adose-dependent increase in hematocrit in the six week study, althoughN47 analog promotes a greater increase in hematocrit compared to rHuEpoat a given concentration. In this experiment the Epo N47 analog is about3 to 4-fold more potent when dosed three times per week byintraperitoneal injection.

Dose response studies of rHuEpo and analog N47 were carried out byintravenous injection three times per week using procedures similar tothose for intraperitoneal injection. The results obtained were similarto those for intraperitoneal administration and, in particular, thestudies further confirmed that Epo N47 analog had a greater potency thanrHuEpo when administered three times per week.

To better compare and quantify the biological activity of rHuEpo and EpoN47 analog in raising the hematocrit of normal mice, results ofexperiments were also analyzed by relative potency plots. For eachexperiment, the activity of rHuEpo or N47 analog at each dose wasdetermined by summing the increase in hematocrit over the first 38 daysof the study by trapezoidal summation to obtain the area under the curve(AUC). This was then plotted versus the log dose in μg peptide/kg/week.Potency difference between compounds administered by the same ordifferent routes of administration or dosing frequencies can bedetermined by measuring the distance between the relevant log-doseresponse lines. FIG. 7 summarizes the relative potency data for allexperiments performed comparing the activity of rHuEpo and Epo N47analog administered by two different routes (intraperitoneal andintravenous) and at two different dosing schedules.

As shown in FIG. 7 when administered three times per week, Epo N47analog has the same potency when injected by either the intravenous orintraperitoneal route and was 3.6-fold more potent than rHuEpo injectedintraperitoneally three times weekly.

Hematocrit Dose Response Studies at One Time Per Week (QW)

Comparisons of rHuEpo and Epo analog N47 at increasing hematocrit innormal mice were undertaken with once weekly dosing by either theintraperitoneal or intravenous routes of administration for six weeks.

Normal CD1 mice weighing approximately 30 g (8-10 mice per group) wereinjected intravenously once weekly for a total of six weeks with varyingconcentrations of either rHuEpo or Epo N47 analog prepared in PBScontaining 0.025% mouse serum albumin, or with vehicle control (PBS with0.025% mouse serum albumin). The analog dose varied from 6.25-25 μg ofpeptide/kg/dose and the dose of rHuEpo varied from 25-200 μg/kg/dose.The hematocrits of all mice were determined at baseline and twice weeklythereafter by retro-orbital bleeds. At the conclusion of the experiment,serum from all animals was collected and assayed for antibodies to theinjected product by a solution radioimmunoprecipitation. Data fromanimals judged to be negative for neutralizing antibodies were used forsubsequent analysis.

As shown in FIG. 8, whereas both rHuEpo and analog N47 can increase thehematocrit of normal mice when dosed once weekly, the dose of rHuEporequired to produce a response was significantly greater than that foranalog N47. For instance, in this experiment 25 μg peptide/kg/week ofN47 increased the hematocrit of mice by 41.2 points in six weeks,whereas the same dose of rHuEpo produced only a 12.5 point hematocritrise.

Dose response studies of rHuEpo and analog N47 were performed byintraperitoneal injection once weekly using procedures similar to thosedescribed above. The results obtained were consistent with the resultsfor intravenous administration and further confirmed the greater potencyof analog N47 compared with rHuEpo when administered one time per week.

To quantify the activity difference between rHuEpo and N47 analog wheneach is dosed once weekly, relative potency plots were generated fromall relevant experiments as described above. As shown in FIG. 7, whenadministered one time per week, analog N47 has the same potency wheninjected by the intravenous and intraperitoneal route. Analog N47 isapproximately 14-fold more potent than rHuEpo when each is administeredonce weekly.

In addition, the log-dose response plots in FIG. 6 also illustrate thefollowing: (1) A given dose of analog N47 administered once weekly (QW)is approximately as effective as the same total weekly dose of rHuEpogiven as three divided doses (TIW); (2) A given dose of rHuEpoadministered once weekly (QW) is only approximately 2% as effective asthe same total weekly dose of analog N47 given as three divided doses(TIW); (3) Analog N47 is approximately 4-fold more potent in mice whenadministered TIW compared to QW.

Hematocrit Dose Response Studies at Every Other Week (EOW)

Experiments were also undertaken to assess the ability of analog N47 toincrease the hematocrit of mice when injected once every other week.Normal CD-1 mice (10 mice per group) were injected intravenously eitheronce weekly or once every other week for a total of approximately sixweeks with varying concentrations of Epo N47 analog prepared in PBScontaining 0.025% mouse serum albumin. Analog N47 was administered ateither 200, 100 or 25 μg/kg/dose every other week or at 12.5 μg/kg/doseonce weekly. The hematocrits of all mice were determined at baseline andtwice weekly thereafter by retroorbital bleeds.

As shown in FIG. 9, analog N47 can increase the hematocrit of normalmice in a dose-dependent fashion even when administered bi-monthly. Asexpected when dosed less frequently, a greater amount of N47 analog isrequired to increase the hematocrit. A dose of 200 μg/kg of N47 analogadministered every other week increased the hematocrit to approximatelythe same extent in six weeks as did 12.5 μg/kg when dosed weekly.

EXAMPLE 6 IV Pharmacokinetics of Epo N47 Analog and rHuEpo in ContinuousAmbulatory Peritoneal Dialysis (CAPD) Patients

In view of the marked increase in serum half-life of Epo N47 analogcompared to rHuEpo in rat and beagle dog, it was of interest todetermine whether an increase could also be observed in humans.

A double-blind, randomized cross-over design study of eleven stable CAPDpatients (7 males, 4 females, aged 27-75 years) was undertaken. Onepatient group received 100 U/kg of rHuEpo (equivalent to 0.5 μg ofpeptide/kg) while a second group of patients received 0.5 μg peptide/kgof Epo N47 analog, both administered as a single bolus injectionintravenous. Venous blood samples (3 mL) were drawn via an indwellingcannula and were taken pre-dose and at 5, 10, 15, 30 minutes and 1, 2,5, 8, 12, 16, 24, 30, 36, 48, 60, 72 and 96 hours after the intravenousbolus. After a 28 day washout period, the first patient group received asingle intravenous dose of Epo analog N47 while the second groupreceived a single intravenous dose of rHuEpo. Blood samples were takenas in the first cycle of treatment. Levels of rHuEpo and Epo N47 analogwere determined in serum by ELISA after subtraction of baselineendogenous Epo levels. The pharmacokinetic parameters (mean±SE)estimated after adjustment for cross-over design effects are shown inTable 5. The serum concentration AUC was calculated using the lineartrapezoidal summation. t1/2_(z) is defined as: log(2)/K_(z), where K_(z)is calculated as the slope of the terminal portion of the ln (serumconcentration) time curve. The clearance (Cl) is defined as: dose/AUC.The volume of distribution (V_(d)) is defined as: Cl/K.

TABLE 5 Dose AUC Cl Group (ng · h/mL) t_(1/2z) (h) (mL/h/kg) Vd (mL/kg)N47 291.0 ± 7.6 25.3 ± 2.2 1.6 ± 0.3 52.4 ± 2.0 rHuEpo 131.9 ± 8.3  8.5± 2.4 4.0 ± 0.3 48.7 ± 2.1

The mean serum half-life for Epo N47 analog (25.3 hr) was three timeslonger than for rHuEpo (8.5 hr) and the clearance was 2.5-fold fasterfor rHuEpo than for analog N47.

EXAMPLE 7 A Phase II Dose Finding and Dose Scheduling Study of Epo N47Analog

Multicenter, randomized, sequential dose-escalation studies areinitiated to investigate the optimum dose and dose schedule for analogN47 when administered by subcutaneous or intravenous injection inpatients with CRF receiving dialysis.

The dosing schedule is as follows:

Once per week dosing: 0.075, 0.225, 0.45, 0.75, 1.5 and 4.5 μg ofpeptide/kg/dose.

Three times per week dosing: 0.025, 0.075, 0.15, 0.25, 0.5 and 1.5 μg ofpeptide/kg/dose.

The studies are carried out in two parts: the first part is adose-escalation study designed to evaluate the dose of analog N47 giveneither one or three times per week which increases hemoglobin at anoptimum rate over four weeks (greater than or equal to 1 g/dL but lessthan 3 g/dL). The second part of each study is designed to determine thedoses required (when administered once or three times per week by eitherthe intravenous or subcutaneous routes of administration) to maintainthe hematocrit at the therapeutic target.

Preliminary results indicate that once weekly dosing with analog N47 canbe used to both increase and maintain the hematocrit of anemic CRFpatients. Initial results suggest that the preferred doses to initiatetherapy on a three times a week dosing schedule are 0.15 and 0.25μg/peptide/kg/dose, and on a one time per week dosing schedule are 0.45and 0.75 μg/peptide/kg/dose for both routes of administration.

While the invention has been described in what is considered to be itspreferred embodiments, it is not to be limited to the disclosedembodiments, but on the contrary, is intended to cover variousmodifications and equivalents included within the spirit and scope ofthe appended claims, which scope is to be accorded the broadestinterpretation so as to encompass all such modifications andequivalents.

1-44. (canceled)
 45. An analog of human erythropoietin comprising theamino acid sequence of human erythropoietin from residues 1-165 as shownin SEQ ID NO:1 except for one or more amino acid changes which providefor one or more additional glycosylation site(s) as compared to humanerythropoietin, wherein one additional site is introduced at position52, 53, 55, 86 or 114 and an N-linked carbohydrate chain is attached atsaid one additional site.
 46. The analog of claim 45 wherein additionalglycosylation sites are introduced at positions 30 and 55 and N-linkedcarbohydrate chains are attached at the additional sites.
 47. The analogof claim 45 wherein additional glycosylation sites are introduced atpositions 30 and 114 and N-linked carbohydrate chains are attached atthe additional sites.
 48. The analog of claim 45 wherein additionalglycosylation sites are introduced at positions 30, 55 and 88 andN-linked carbohydrate chains are attached at the additional sites. 49.The analog of claim 45 wherein additional glycosylation sites areintroduced at positions 30, 55 and 114 and N-linked carbohydrate chainsare attached at the additional sites.
 50. The analog of claim 45 whereinadditional glycosylation sites are introduced at positions 30, 88 and114 and N-linked carbohydrate chains are attached at the additionalsites.
 51. The analog of claim 45 wherein additional glycosylation sitesare introduced at positions 30, 55, 88 and 114 and an N-linkedcarbohydrate chain is attached at the additional sites.
 52. The analogof claim 45 further comprising an additional glycosylation site atposition 125 and wherein an O-linked carbohydrate chain is attached atthe additional site.
 53. The analog of claim 45 comprising three, four,or more than four additional glycosylation sites wherein a carbohydratechain is attached at the additional sites.
 54. An analog of humanerythropoietin comprising the amino acid sequence from residues 1-165 asshown in SEQ ID NO:1 except for Asn at position 30, Thr at position 32,Asn at position 55, Thr at position 57, Val at position 87, Asn atposition 88, Thr at position 90, Asn at position 114, Thr at position116, and any one or more of Pro at position 124, Thr at position 125and/or Thr at position
 126. 55. An analog of human erythropoietincomprising the amino acid sequence from residues 1-165 as shown in SEQID NO:1 except for the amino acid changes selected from the groupconsisting of: Asn⁵² Thr⁵⁴ Epo; Asn⁵³ Thr⁵⁴ Epo; Asn³⁰ Thr³² Val⁸⁷ Asn⁸⁸Thr⁹⁰ Thr¹²⁵ Epo; Asn¹¹⁴ Thr¹¹⁶ Epo; Asn³⁰ Thr³² Asn⁵³ Thr⁵⁵ Val⁸⁷Asn⁸⁸Thr⁹⁰ Epo; Asn⁵⁵ Thr⁵⁷ Epo; Asn⁸⁶ Val⁸⁷ Thr⁸⁸ Epo; Ala⁸⁷ Asn⁸⁸Thr⁹⁰ Epo; Val⁸⁷ Asn⁸⁸ Ser⁹⁰ Epo; Val⁸⁷ Asn⁸⁸ Gly⁸⁹ Thr⁹⁰ Epo; Asn³⁰Thr³² Asn⁵³ Thr⁵⁵ Epo; Asn³⁰ Thr³² Asn¹¹⁴ Thr¹¹⁶ Epo; Asn³⁰ Thr³² Asn⁵³Thr⁵⁵ Val⁸⁷ Asn⁸⁸ Thr⁹⁰ Asn¹¹⁴ Thr¹¹⁶ Epo; Asn³⁰ Thr³² Asn⁵⁵ Thr⁵⁷ Epo;Asn³⁰ Thr³² Asn⁵⁵ Thr⁵⁷ Val⁸⁷ Asn⁸⁸ Thr⁹⁰ Epo; Asn³⁰ Thr³² Asn⁵⁵ Thr⁵⁷Asn¹¹⁴ Thr¹¹⁶ Epo; Asn³⁰ Thr³² Val⁸⁷ Asn⁸⁸ Thr⁹⁰ Asn¹¹⁴ Thr¹¹⁶ Epo;Asn³⁰ Thr³² Asn⁵⁵ Thr⁵⁷ Val⁸⁷ Asn⁸⁸ Thr⁹⁰ Asn¹¹⁴ Thr¹¹⁶ Epo; Asn³⁰ Thr³²Asn⁵⁵ Thr⁵⁷ Val⁸⁷ Asn⁸⁸ Thr⁹⁰ Pro¹²⁴ Thr¹²⁵ Thr¹²⁶ Epo; Asn³⁰ Thr³²Asn⁵⁵ Thr⁵⁷ Asn¹¹⁴ Thr¹¹⁶ Pro¹²⁴ Thr¹²⁵ Thr¹²⁶ Epo; and Asn³⁰ Thr³²Asn⁵⁵ Thr⁵⁷ Val⁸⁷ Asn⁸⁸ Thr⁹⁰ Asn¹¹⁴ Thr¹¹⁶ Pro¹²⁴ Thr¹²⁵ Thr¹²⁶ Epo.56. The analog of claims 45, 54 or 55 which is the product of expressionof an exogenous DNA sequence.
 57. A composition comprising atherapeutically effective amount of an analog of claim 45 and apharmaceutically acceptable diluent, carrier, solubilizer, emulsifier,preservative, anti-oxidant and/or adjuvant.
 58. The composition of claim57 wherein the diluent is Tris, citrate, acetate or phosphate buffer.59. The composition of claim 57 wherein the carrier is human albumin orgelatin.
 60. The composition of claim 57 wherein the solubilizer istween or polysorbate.
 61. The composition of claim 57 wherein thepreservative is thimerosal, parabens, benzylalconium chloride or benzylalcohol.
 62. The composition of claim 57 wherein the antioxidant isascorbic acid or sodium metabisulfite.
 63. The composition of claim 57further comprising an amino acid.
 64. The composition of claim 63wherein the amino acid is lysine or glycine.
 65. The composition ofclaim 57 which is in liquid or lyophilized form.